but if I did I'd not be expecting my dog to meet any othersI'm in total agreement, my groomer always has dogs seperated unless from the same family. What if there is a dog aggressive adult there, doesn't bare thinking about does it?
she said he was getting in the other dog's faces and barking at them, also growling.
I can't tell you how normal this is, it is what pups of this age do it is how they learn, how they play, if your pup were still with it's siblings they would be growling, tugging, scratching, pulling each other around by the ear and pouncing all over each other making the most terrible noises, looking very aggressive, but not a drop of blood or a scratch would appear, they would then lick and cuddle up to each other to sleep and play less aggressive games too.

We take our pups away from their siblings and domesticate them to live with us but that does not stop their natural instinct to behave as they should do, pups are veeing for their pecking orders even at this young age and through aggressive play they are weighing each other up, it is not acceptable to us but to dogs it is perfectly normal.
90% of adult dogs will ignore a puppies play, some will run away from them, some give a quiet growl to indicate "Leave me alone!" He only has his growls to indicate unhappiness it is his way of speaking, so when your children pick him up when tired he is only telling them to leave
him alone, make sure he has his own space to escape to as well, and if over excited pop him in time out to calm down.
(If someone can add the link
The Bite Stops Here) You will also find it invaluable.
But please don't worry your pup is perfectly normal and the groomer needs to just groom, I certainly would not go back to anyone who was giving out a negative and making you worry your pup is not normal, not exactly helpful was she, give her a wide berth.